==Texts. phrases, and utterances== The outermost linguistic structure is ``Text``. ``Text``s are composed from Phrases (``Phr``) followed by punctuation marks - either of ".", "?" or "!" (with their proper variants in Spanish and Arabic). Here is an example of a ``Text`` string. ``` John walks. Why? He doesn't want to sleep! ``` Phrases are mostly built from Utterances (``Utt``), which in turn are declarative sentences, questions, or imperatives - but there are also "one-word utterances" consisting of noun phrases or other subsentential phrases. Some Phrases are atomic, for instance "yes" and "no". Here are some examples of Phrases. ``` yes come on, John but John walks give me the stick please don't you know that he is sleeping a glass of wine a glass of wine please ``` There is no connection between the punctuation marks and the types of utterances. This reflects the fact that the punctuation mark in a real text is selected as a function of the speech act rather than the grammatical form of an utterance. The following text is thus well-formed. ``` John walks. John walks? John walks! ``` What is the difference between Phrase and Utterance? Just technical: a Phrase is an Utterance with an optional leading conjunction ("but") and an optional tailing vocative ("John", "please"). ==Sentences and clauses== TODO: use overloaded operations in the examples. The richest of the categories below Utterance is ``S``, Sentence. A Sentence is formed from a Clause (``Cl``), by fixing its Tense, Anteriority, and Polarity. For example, each of the following strings has a distinct syntax tree in the category Sentence: ``` John walks John doesn't walk John walked John didn't walk John has walked John hasn't walked John will walk John won't walk ... ``` whereas in the category Clause all of them are just different forms of the same tree. The difference between Sentence and Clause is thus also rather technical. It may not correspond exactly to any standard usage of the terms "clause" and "sentence". Figure 1 shows a type-annotated syntax tree of the Text "John walks." and gives an overview of the structural levels. #BFIG ``` Node Constructor Value type Other constructors ----------------------------------------------------------- 1. TFullStop Text TQuestMark 2. (PhrUtt Phr 3. NoPConj PConj but_PConj 4. (UttS Utt UttQS 5. (UseCl S UseQCl 6. TPres Tense TPast 7. ASimul Anter AAnter 8. PPos Pol PNeg 9. (PredVP Cl 10. (UsePN NP UsePron, DetCN 11. john_PN) PN mary_PN 12. (UseV VP ComplV2, ComplV3 13. walk_V)))) V sleep_V 14. NoVoc) Voc please_Voc 15. TEmpty Text ``` #BCENTER Figure 1. Type-annotated syntax tree of the Text "John walks." #ECENTER #EFIG Here are some examples of the results of changing constructors. ``` 1. TFullStop -> TQuestMark John walks? 3. NoPConj -> but_PConj But John walks. 6. TPres -> TPast John walked. 7. ASimul -> AAnter John has walked. 8. PPos -> PNeg John doesn't walk. 11. john_PN -> mary_PN Mary walks. 13. walk_V -> sleep_V John sleeps. 14. NoVoc -> please_Voc John sleeps please. ``` All constructors cannot of course be changed so freely, because the resulting tree would not remain well-typed. Here are some changes involving many constructors: ``` 4- 5. UttS (UseCl ...) -> UttQS (UseQCl (... QuestCl ...)) Does John walk? 10-11. UsePN john_PN -> UsePron we_Pron We walk. 12-13. UseV walk_V -> ComplV2 love_V2 this_NP John loves this. ``` ==Parts of sentences== The linguistic phenomena mostly discussed in both traditional grammars and modern syntax belong to the level of Clauses, that is, lines 9-13, and occasionally to Sentences, lines 5-13. At this level, the major categories are ``NP`` (Noun Phrase) and ``VP`` (Verb Phrase). A Clause typically consists of just an ``NP`` and a ``VP``. The internal structure of both ``NP`` and ``VP`` can be very complex, and these categories are mutually recursive: not only can a ``VP`` contain an ``NP``, ``` [VP loves [NP Mary]] ``` but also an ``NP`` can contain a ``VP`` ``` [NP every man [RS who [VP walks]]] ``` (a labelled bracketing like this is of course just a rough approximation of a GF syntax tree, but still a useful device of exposition). Most of the resource modules thus define functions that are used inside NPs and VPs. Here is a brief overview: **Noun**. How to construct NPs. The main three mechanisms for constructing NPs are - from proper names: "John" - from pronouns: "we" - from common nouns by determiners: "this man" The ``Noun`` module also defines the construction of common nouns. The most frequent ways are - lexical noun items: "man" - adjectival modification: "old man" - relative clause modification: "man who sleeps" - application of relational nouns: "successor of the number" **Verb**. How to construct VPs. The main mechanism is verbs with their arguments, for instance, - one-place verbs: "walks" - two-place verbs: "loves Mary" - three-place verbs: "gives her a kiss" - sentence-complement verbs: "says that it is cold" - VP-complement verbs: "wants to give her a kiss" A special verb is the copula, "be" in English but not even realized by a verb in all languages. A copula can take different kinds of complement: - an adjectival phrase: "(John is) old" - an adverb: "(John is) here" - a noun phrase: "(John is) a man" **Adjective**. How to constuct ``AP``s. The main ways are - positive forms of adjectives: "old" - comparative forms with object of comparison: "older than John" **Adverb**. How to construct ``Adv``s. The main ways are - from adjectives: "slowly" - as prepositional phrases: "in the car" ==Modules and their names== This section is not necessary for users of the library. TODO: explain the overloaded API. The resource modules are named after the kind of phrases that are constructed in them, and they can be roughly classified by the "level" or "size" of expressions that are formed in them: - Larger than sentence: ``Text``, ``Phrase`` - Same level as sentence: ``Sentence``, ``Question``, ``Relative`` - Parts of sentence: ``Adjective``, ``Adverb``, ``Noun``, ``Verb`` - Cross-cut (coordination): ``Conjunction`` Because of mutual recursion such as in embedded sentences, this classification is not a complete order. However, no mutual dependence is needed between the modules themselves - they can all be compiled separately. This is due to the module ``Cat``, which defines the type system common to the other modules. For instance, the types ``NP`` and ``VP`` are defined in ``Cat``, and the module ``Verb`` only needs to know what is given in ``Cat``, not what is given in ``Noun``. To implement a rule such as ``` Verb.ComplV2 : V2 -> NP -> VP ``` it is enough to know the linearization type of ``NP`` (as well as those of ``V2`` and ``VP``, all given in ``Cat``). It is not necessary to know what ways there are to build ``NP``s (given in ``Noun``), since all these ways must conform to the linearization type defined in ``Cat``. Thus the format of category-specific modules is as follows: ``` abstract Adjective = Cat ** {...} abstract Noun = Cat ** {...} abstract Verb = Cat ** {...} ``` ==Top-level grammar and lexicon== The module ``Grammar`` collects all the category-specific modules into a complete grammar: ``` abstract Grammar = Adjective, Noun, Verb, ..., Structural, Idiom ``` The module ``Structural`` is a lexicon of structural words (function words), such as determiners. The module ``Idiom`` is a collection of idiomatic structures whose implementation is very language-dependent. An example is existential structures ("there is", "es gibt", "il y a", etc). The module ``Lang`` combines ``Grammar`` with a ``Lexicon`` of ca. 350 content words: ``` abstract Lang = Grammar, Lexicon ``` Using ``Lang`` instead of ``Grammar`` as a library may give for free some words needed in an application. But its main purpose is to help testing the resource library, rather than as a resource itself. It does not even seem realistic to develop a general-purpose multilingual resource lexicon. The diagram in Figure 2 shows the structure of the API. #BFIG #GRAMMAR #BCENTER Figure 2. The resource syntax API. #ECENTER #EFIG ==Language-specific syntactic structures== The API collected in ``Grammar`` has been designed to be implementable for all languages in the resource package. It does contain some rules that are strange or superfluous in some languages; for instance, the distinction between definite and indefinite articles does not apply to Finnish and Russian. But such rules are still easy to implement: they only create some superfluous ambiguity in the languages in question. But the library makes no claim that all languages should have exactly the same abstract syntax. The common API is therefore extended by language-dependent rules. The top level of each languages looks as follows (with English as example): ``` abstract English = Grammar, ExtraEngAbs, DictEngAbs ``` where ``ExtraEngAbs`` is a collection of syntactic structures specific to English, and ``DictEngAbs`` is an English dictionary (at the moment, it consists of ``IrregEngAbs``, the irregular verbs of English). Each of these language-specific grammars has the potential to grow into a full-scale grammar of the language. These grammars can also be used as libraries, but the possibility of using functors is lost. To give a better overview of language-specific structures, modules like ``ExtraEngAbs`` are built from a language-independent module ``ExtraAbs`` by restricted inheritance: ``` abstract ExtraEngAbs = Extra [f,g,...] ``` Thus any category and function in ``Extra`` may be shared by a subset of all languages. One can see this set-up as a matrix, which tells what ``Extra`` structures are implemented in what languages. For the common API in ``Grammar``, the matrix is filled with 1's (everything is implemented in every language). Language-specific extensions and the use of restricted inheritance is a recent addition to the resource grammar library, and has only been exploited in a very small scale so far.